1. Field of the Invention
The present invention generally relates to a cooling system for a lubricating system of an internal combustion engine. More particularly, the present invention relates to a cooling system for a lubricating system of a watercraft engine that powers a water propulsion device.
2. Description of Related Art
Personal watercraft have become very popular in recent years. An enthusiasm for competition has grown with this popularity, and as a result personal watercraft have become increasingly fast. Many personal watercraft today are capable of speeds well in excess of 60 miles per hour. To attain such speeds, such watercraft are typically driven by high power output motors.
Two-cycle engines commonly power personal watercrafts, as these engines have the advantage of being fairly powerful and relatively light and compact. One particular disadvantage of two-cycle engines though is emission content. Two-cycle engines exhaust large quantities of carbon monoxide and various hydrocarbons. However, when steps are taken to reduce the emission content of a two-cycle engine, other generally undesirable consequences result, such as an increase in the weight of the engine and reduction of its power output.
Four-cycle engines have now been proposed as the power plant for personal watercrafts. These engines have the advantage of less hydrocarbon emission than a two-cycle engine while maintaining a relatively high power output.
It is therefore desirable to provide a watercraft with a four-cycle engine in order to reduce exhaust emissions without significantly impacting the power output of the engine that powers the watercraft.
The present invention involves in part the recognition that several problems arise in connection with employing a four-cycle engine within a personal watercraft. One such problem involves the fact that four-cycle engines are generally arranged with oil-filled crankcases or reservoirs positioned at the bottom of the cylinder block. When this type of engine is mounted in a personal watercraft, the associated oil pump may not consistently draw oil from the crankcase as the oil sloshes from side to side with abrupt maneuvers of the watercraft. In addition, because of the confined space of the engine compartment and a desire to inhibit water influx into the water compartment, the engine typically runs hot. Running such a motor at a very high output exacerbates the heat of the engine. If the motor is continuously run in this manner, the lubricants viscosity will break down and will not be able to properly cool and lubricate the engine. In extreme cases, viscosity breakdown can result in the engine overheating and seizure.
The present invention therefore provides a lubrication system with a cooling system so as to prevent overheating of the lubricant and viscosity breakdown of the lubricant.
One aspect of the present invention therefore involves a small watercraft comprising a hull with an engine compartment, and an internal combustion engine, located within the hull, which has an output shaft. A propulsion device is carried by the hull and is driven by the engine output shaft to propel the watercraft. The engine also includes a lubrication system including a pump and a reservoir, the lubrication system circulating lubricant between the engine and the reservoir. A cooling jacket, in contact with at least a portion of the reservoir, draws heat away from the reservoir, thereby cooling the reservoir and the lubricant contained therein.
In accordance with a further aspect of the present invention, a watercraft is provided comprising a hull with an engine compartment, and an internal combustion engine, located within the hull, which has an output shaft. A propulsion device is carried by the hull and is driven by the engine output shaft to propel the watercraft. The engine also includes a lubrication system including a pump and a reservoir, the lubrication system circulating lubricant between the engine and the reservoir. At least a portion of the reservoir is in direct contact with the ambient fluid in which the watercraft floats, such that the ambient fluid is able to absorb heat from the reservoir, thereby cooling the reservoir and the lubricant contained therein.
In accordance with a further aspect of the present invention, a watercraft is provided comprising a hull with an engine compartment, and an internal combustion engine, located within the hull, which has an output shaft. A propulsion device is carried by the hull and is driven by the engine output shaft to propel the watercraft. The engine also includes a lubrication system including a pump and a reservoir, the lubrication system circulating lubricant between the engine and the reservoir. At least a portion of the reservoir is contact with a material having good heat-transfer characteristics, this material also being in contact with the ambient fluid in which the watercraft floats, such that the material transfers heat from the reservoir to the ambient fluid, thereby cooling the reservoir and the lubricant contained therein.
Further aspects, features, and advantages of the present invention will become apparent from the detailed description of the preferred embodiments which follow.